Telephonic appliance.



No. 665,923. Patented Jan. l5, l90l.

F. R. McBEBTY.

' TELEPHONIC APPLIANCE.

(Application filed Aug. 12, 1397.

(No Model.)

KIIIIIIIIIIIHHrJm p NlTE D STATES PATENT OFFICE.

FRANK R. MCBERTY, OF DOWNERS GROVE, ILLINOIS, ASSIGNOR TO THE WESTERN ELECTRIC COMPANY, OF CHICAGO, ILLINOIS.

TELEPHCNIC APPLIANCE.

SPECIFICATION forming part of Letters Patent No. 665.923, dated January 15, 1901. Application filed August 12, 1897. Serial No. 647,941. (No model.)

To all whom it may concern.-

Be it known that l, FRANK R. MCBERTY, a citizen of the United States, residing at Downers Grove, in the county of Du Page and State of Illinois, have invented a certain new and useful Improvement in Telephonic Appliances, (Case No. 54,) of which the following is a full, clear, concise, and exact description, reference being had to the accompanying drawings, forming a part of this specification.

This invention concerns electromagnets with closed magnetic circuits for use in circuits carrying telephonic or other rapidly alternating or undulating currents, its object being to prevent the inductive propagation of corresponding currents in neighboring circuits or magnets. It is useful particularly in connection with signal magnets or repeating-coils in telephonic circuits, since these are commonly placed close together in large groups and since each circuit must be entirely free from inductive disturbances from other circuits.

When electroinagnets interposed directly in telephonic circuits or located in bridges of such circuits are placed near together, it is found that although the magnetic or iron circuit of the magnet may beclosed through a mass of iron of large cross-section there is still a considerable amount of magnetic leakage from the extremities of the circuit or stray lines of force. These linesof force seek a return through the magnetic circuits of neighboring magnets, and thus tend to induce disturbing currents in the circuits surrounding the cores of neighboring magnets. This is true not only of electromagnets with movable armatures, but of impedance-coils and induction-coils whether of the open-circuit or closed-circuit type. The present invention expedient inoperative.

of conducting material is to prevent the propagation of these lines of force into adjacent magnet cores or circuits by permitting them to expend their energy in inducing currents in the conducting mass. For instance, in the case of a closed-circuit electromagnet surrounded by a copper tube the lines of force which circulate within the closed magnetic circuit are not afiected or disturbed by the copper tube, and thus serve with undiminished efficiency to perform any Work required; but the stray lines of force emanating from projecting or prominent portions of the magnetic circuit and tending to return through the air or adjacent masses of magnetic material thread the encircling copper tube but once, and therefore induce currents in the copper tube which tend to suppress the rapidly alternating or undulating induction. Thus in the case of two adjacent electromagnets in telephonic circuits which are ordinarily characterized by strong cross-talk rising through their mutual induction the cross-talk may be perfectly suppressed and eliminated by surrounding either, or preferably both, of the closed magnetic circuits with thick tubes of conducting material.

Heretofore in telephonic signal-magnets designed to be used in bridges of telephone-circuits it has been common to construct the magnets in tubular form, the tubular shells of the magnets being continuous cylinders.

In such magnets the impedance of the magnet has been greatly diminished by the currents inducedin the tubular shell of the magnet; but when an attempt has been made to interrupt the continuity of the electric circuit in the shell, as by slitting the shell longitudinally, the cross-talk produced in the circuits of adjacent magnets has rendered this The present invention is based on the discovery of the reason for the freedom of tubular magnets from cross-talk, and its application permits the slitting of the shells to break the induced currents therein, so that the magnet not only possess es the maximum. impedance, but is also free from external inductive action.

The invention is illustrated indifierent forms inthe attached drawings, whereof- Figure 1 is a side elevation of a group of tial section.

including signal-controlling relays and impedance-coils.

The signal-controlling relay comprises a core a with wire I) wound thereon, which is arranged centrally in a tubular shell (3- of iron, one end of the shell being closed with a cap of magnetic material. This shell is constructed from sheet metal folded in tubular form, the edges, however, being separated by a slight distance. The object of this mode of constructing the shell is in the present instance merely for the sake of economy, inasmuch as shells folded from sheet metal are very much cheaper and simpler to manufacture than continuous tubes; but in the case of similar relays adapted for use in bridges of telephone-circuits wherein the impedance of the elcctromagnet is of importance the tubular slit shell forms a suitable return-circuit for the magnetic lines of force, while being itself a broken electric circuit to electromotive forces created in it by induction.

Opposite the exposed or polar extremity of the core and shell is placed an'armaturedisk (1, ordinarily retained in vertical position and resting on its edge, so as to rock toward the magnet in response to the attraction of the core and shell exerted upon it. Suitable insulated contact-pieces are provided for the armature to be closed when the armature .is attracted. Several of these relays are mounted on a common base 6, anda large number of relays are ordinarily grouped as compactly as -.-possible.

Followingthe present invention, a copper tube fis placed over the tubular shell of each magnet.

'The impedance-coil represented in Figs. 3

and lcoinprises merely a closed or ring circuit of iron Wire g, of which a portion is surrounded by one or more windings h of wire, adapted for inclusion in elect-riccircuits. In fitting this device with the present invention a copper tube or ring 1' is placed over the closed magnetic circuit, embracing the complete circuit. I

When either of the before-described appliancesthe magnet or the impedance-coil-is included in the telephone-circuitQthe lines of force produced by current circulating in the magnet-windings do not wholly traverse the iron circuit-provided for them. A few tend to stray or emanate from prominent or projecting portions of the iron circuit and to find return-circuits through-neighboring magnets or electricalcircuits. When, however, these lines of force are of rapidly fluctuating or alternating character, they expend their energy in inducing current in the copper shells Fig. 3 is a side elevation of fand t,-respectively, and are almost wholly suppressed thereby.

In the case of the impedance-coil or of the magnet designed to present great impedance to telephonic current through its winding the lines of force useful as impedance circulate I wholly in the iron of the magnetic circuit,

and thus since they are wholly contained within the copper tube, or thread it twice in opposite directions, they induce no currents therein.

Fig. 5 represents plug-circuits adapted for use in telephone-switchboards, each comprising a pair of connecting-plugs 7e and l, united by conductors 1 2, from the point of junction of which a ground branch 3 is led to battery m. trolling magnet n is interposed, while in each ground branch 3 an impedance-coil o is located. When a pair of plugs is in use, current flows through the impedance-coil 0 to the plug-circuit and thence to the telephones at the" united stations. The telephonic undulations in this current produced by the substation transmittin'g-telephones are not-propagated to any appreciable extent through the impedance-coil 0 on account of the impedance thereof. The copper tube iabout the impedance-coil prevents the induction of like undulations in adjacent impedance-coils. The telephonic currents traverse the windings of the signal-controlling magnets it, however, the windings of these magnets being of low resistance, and produce correspondingly undulating magnetization therein. The mag netic circuits of these magnets are complete with the encircling copper tubes, so that the magnets serve efficiently to do whatever work is required of them, while in this case also the copper tubes prevent induction between adjacent magnets.

I claim as my invention- 1. The combination with a core of magnetic material and a magnetizing'winding therefor, of a mass of magnetic material forming a return-circuit for the lines of force emanating from said core, whereby a complete magnetic ing circuit encircling the core and the returncircuit, substantially as described.

2. The combination with a mass of magnetic material formed to constitute a substantially closed complete magnetic circuit, of a magnetizing winding surrounding a portion of said magnetic material to produce induction in the circuit, the remainder of said magnetic material forming a return-circuit for the lines of force emanating from the portion surrounded by said windin g, and a closed circuit of electrically-conducting material inclosing substantially the entire magnetic circuit, whereby the lines of force are confined to the aforesaid closed magnetic circuit provided'for them, substantially as set forth.

3. The combination with a telephone-circuit, of an electromagnet having a substantially closed magnetic circuit and a winding In each conductor 1 and 2 a signal-concircuit is formed, and an electrically-conduct-,

on one limb only of said magnetic circuit in the telephone-circuit, and a closed electrical circuit of low resistance associated with the electromagnet in position to be threaded by lines of force straying from the portions of the magnetic circuit not covered by the Winding, substantially as described.

4. The combination with telephone-circuits and magnet-windings therein located near one another, of masses of magnetic material arranged in substantially closed complete magnetic circuits, the said magnet-windings surrounding portions of said magnetic circuits to produce induction therein, the portions not so surrounded forming return-paths for the lines of force, and closed circuits of electrically-conducting material having low resistance, interposed between said magnets and adapted to be cut by lines of force between one magnet and another, to shield each magnet from the lines of force of other magnets, substantially as described.

5. The combination with an electromagnet comprising a mass of magnetic material arranged in a substantially closed complete magnetic circuit, and a magnetizing-winding surrounding a portion of such circuit, the portion not so surrounded forming a return-path for thelines of force, of a tube or ring of copper inclosing substantially the entire magnetic circuit, as described.

6. The combination with telephone-circuits and electromagnetic appliances therein, each such appliance comprising a practicallyclosed magnetic circuit and an exciting-winding in the telephone-circuit encircling a limb of said magnetic circuit, said appliances being contiguous to one another, of a tube of copper surrounding both limbs of the closed magnetic circuit of each appliance, whereby cross-talk between the appliances is pre- Vented.

7. The combination with a tubular magnet comprising a magnetic core, a magnetizingwinding surrounding the same, and a tubular shell of magnetic material inclosing the core and its winding, said shell being united with the core and forming a return-path for the lines of force emanating from said core, of a copper tube inclosing the tubular shell of said magnet, substantially as and for the purpose set forth.

8. The combination with a tubular magnet having a shell longitudinally slit to prevent eddy-currents, and the armature thereof, of a tube of copper surrounding the shell, as described.

9. The combination with a telephone-circuit and a'closed bridge thereof, and a tubular magnet having its Winding in the said bridge and provided with a shell longitudinally slit to prevent eddy-currents, of a tube of copper surrounding the said shell; whereby the impedance of the magnet in the bridge is increased, while cross-talk from the magnet is prevented, as described.

10. The combination with a magnet comprising a core and the winding thereon, an armature for the core and magnetic material forming a return-circuit for the lines of force between the core and the armature, of acopper tube encircling the said core and returncircuit, as described.

11. The combination with a telephone-circuit and a closed bridge thereof, an electromagnet having a substantially closed magnetic circuit in the said bridge, the magnetic circuit of the electromagnet being formed to prevent the formation of eddy-currents by changes of current in the magnet-winding, of a shell of good conducting material surrounding the closed magnetic circuit, as described.

In witness whereof I hereunto subscribe my name this 18th day of May, A. D. 1897.

\ FRANK R. MCBERTY.

Witnesses:

ELLA EDLER, GENEVA STEVENS. 

